To examine whether Cl-coupled HCO3 transport mechanisms were present on the basolateral membrane of the mammalian proximal tubule, cell pH was measured in the microperfused rat proximal convoluted tubule using the pH-sensitive, intracellularly trapped fluorescent dye (2',7')-bis(carboxyethyl)-(5,6)-carboxyfluorescein. Increasing the peritubular Cl concentration from 0 to 128.6 meq/liter caused ...

OBJECTIVE To review the normal human acid-base physiology and the pathophysiology and management of acid-base disturbances in a two-part presentation. DATA SOURCES Articles and published peer-review abstracts and a review of studies reported from 1990 to 2000 and identified through a MEDLINE search of the English language literature on acid-base balance. SUMMARY OF REVIEW Acid-base disorder...

Pancreatic duct cells secrete a HCO3-rich ( 140 mM) fluid. Using a computer model of the pancreatic duct, Sohma, et al. have demonstrated that the activity of a Cl/ HCO3 exchanger with a 1 : 1 stoichiometry at the apical membrane would have to be suppressed in order to achieve such a HCO3-rich secretion. Recently the apical exchanger in pancreatic ducts has been identified as SLC26A6 and this p...

The epithelial anion channel CFTR interacts with multiple PDZ domain-containing proteins. Heterologous expression studies have demonstrated that the Na+/H+ exchanger regulatory factors, NHERF1, NHERF2, and PDZK1 (NHERF3), modulate CFTR membrane retention, conductivity, and interactions with other transporters. To study their biological roles in vivo, we investigated CFTR-dependent duodenal HCO3...

values. Thanks to a more detailed statistical analysis, Bushinsky et al. show that, by restricting the range of HCO3 values to a maximum of 10 mEq/L, the slope of the linear regression acquires a value of 1.5 (exactly the same slope reported by Winters), while the slope reaches 1.2 for values of HCO3 between 10.1 and 25 mEq/L. To summarise, in our opinion, the more accurate way to predict the e...

Gastric HCO3(-) transport (basal) studied in isolated amphibian mucosa and mammalian stomach in vivo amounts to 2-10% of maximal H+ secretion. Duodenal mucosa, devoid of Brunner's glands, transports HCO3(-) at a greater rate (per unit surface area) than either stomach or jejunum in vitro and in vivo. Gastric (but not duodenal) HCO3(-) transport is stimulated by dibutyryl cGMP, carbachol, and ch...

The midpoint potential (Em) of [Formula: see text], the one-electron acceptor quinone of Photosystem II (PSII), provides the thermodynamic reference for calibrating PSII bioenergetics. Uncertainty exists in the literature, with two values differing by ∼80 mV. Here, we have resolved this discrepancy by using spectroelectrochemistry on plant PSII-enriched membranes. Removal of bicarbonate (HCO3-)...

Because endothelin receptor inhibition blunts increased distal tubule acidification induced by dietary acid, we examined whether endothelin-1 (ET-1) increases acidification of in vivo perfused distal tubules of anesthetized rats. ET-1 was infused intra-aortically (1.4 pmol ⋅ kg-1 ⋅ min-1) into control animals and into those with increased distal tubule HCO3 secretion induced by drinking 80 mM N...

Isometrically mounted and electrically paced myocardial ventricular strips of carp have a much higher capacity to develop force during severe hypoxia and to redevelop force after it than those of rainbow trout. When the concentrations of CO2 and HCO3-in the solutions surrounding the strips were increased together, such that pH remained constant, the force developed during hypoxia increased. The...

This study was designed to determine the effects of colloidal bismuth subcitrate De-Nol on gastric HCO3- secretion in 24 healthy subjects and on gastric and duodenal HCO3- secretion in dogs with gastric and duodenal fistulae. Alkaline secretion was measured after pretreatment with ranitidine to abolish the H+ secretion using a constant perfusion aspiration system and back titration of the perfu...